Examining the cascading effects of changing species interactions on nutrient and energy cycling

Spotlight: Amanda Koltz, PhD | Dept. of Biology

Contributed by Bennett Rosenberg on June 9, 2020.

Dr. Amanda Koltz, a postdoctoral scientist and global change ecologist, has been researching how communities and ecosystems respond to climate change for over a decade. While there has been a lot of attention paid to the devastating species extinctions brought about by climate change, the subject of much of Koltz’s observational and experimental research, the arctic wolf spider, is currently not at risk of extinction. Her work highlights why it is also important to study species that are able to quickly adapt to changing environmental conditions. For example, she is finding some important changes in wolf spider behavior that may have subtle, cascading effects on food webs and arctic ecosystems.

Why study wolf spiders? Beyond admitting some intrinsic interest in arthropods, Koltz notes how they are highly responsive to changes in their environment such as temperature, they develop quickly compared to vertebrates, and that they play important roles within the ecosystem through their predator-prey relations. The Arctic is an excellent study region to ask how wolf spiders respond to climate change and how this will affect their interactions with other species, because wolf spiders are among the most dominant predators there, and because the Arctic is the most rapidly warming biome on Earth.

A mother wolf spider carrying her spiderlings.
Koltz and crew sampling experimental plots near Toolik Field Station, Alaska.

Koltz has made some interesting findings, but much remains unknown. As the Arctic warms, wolf spiders are becoming larger. This increases the amount of eggs that females are able to produce and therefore may also lead to higher wolf spider population densities. However, Koltz has observed that higher population densities also cause increased competition among wolf spiders and lead to higher rates of spider cannibalism. This suggests that wolf spiders regulate their own populations and that they may turn to cannibalism more often in the future as spider reproduction further increases. It also raises questions about whether bigger spiders will lead to larger populations or not in a warming arctic.

Figuring out whether or not climate change will cause larger wolf spider populations in the Arctic is important, because changes in wolf spider interactions can affect the entire food web by strengthening or weakening feedback cycles to climate change itself. Koltz’s research has shown that when there are more wolf spiders, they prey more heavily on lower trophic levels, which indirectly increases the ecosystem’s decomposition. However, the cascading effects of these wolf spiders on the ecosystem is different under warming. When the tundra is experimentally warmed, Koltz has found that less decomposition occurs where there are more wolf spiders due to a change in the strength of wolf spider predation on their prey. This suggests that carbon losses from arctic soils due to warming could potentially be buffered if wolf spider populations also increase in the future.

The team gears up with “bug shirts” to protect from the incredibly dense populations of mosquitoes in the Arctic.
Amanda Koltz in the field.

Below is coverage from some of Koltz’s recent work in Washington University’s The Source:

Relevant Publications:

Høye, TT, Kresse, JC, Koltz, AM and J Bowden. In press. Earlier springs enable High-Arctic wolf spiders to produce a second clutch. Proceedings of the Royal Society B.

Koltz, AM, and JP Wright. 2020. Impacts of female body size on cannibalism and juvenile abundance in a dominant arctic spider. Journal of Animal Ecology 00: 1-11. DOI:10.1111/1365-2656.13230

Koltz, AM, Culler, LE, Bowden, JJ, Post, E, and TT Høye. 2019. Dominant arctic predator is free of major parasite at northern edge of its range. Frontiers in Ecology and Evolution 7:250. DOI: 10.3389/fevo.2019.00250

Gillespie, MAK, Alfredsson, M, Barrio, I, Bowden, J, Koltz, AM, Convey, P, Culler, LE, Coulson, SJ, Henning Krogh, P, Koponen, S, Loboda, S, Marusik, Y, Sandström, JP, Sikes, DS, and TT Høye. 2019. Status and trends of terrestrial arthropod diversity in the North Atlantic region of the Arctic. Ambio, pp. 1-14. DOI: 10.1007/s13280-019-01162-5

Koltz, AM, Classen, A and JP Wright. 2018. Warming reverses top-down effects of predators on the structure and function of belowground communities in the Arctic. Proceedings of the National Academy of Sciences, 201808754. DOI: 10.1073/pnas.1808754115 

Koltz, AM, Schmidt, NM, and TT Høye. 2018. Differential arthropod responses to warming are altering the structure of arctic communities. Royal Society Open Science, 5(4): 171503. DOI: 10.1098/rsos.171503

Koltz, AM, Asmus, AA, Gough, L, Pressler, Y, and JC Moore. 2018. The detritus-based microbial-invertebrate food web contributes disproportionately to carbon and nitrogen cycling in the Arctic. Polar Biology, 41:1531. DOI: 10.1007/s00300-017-2201-5

Asmus, AA, Koltz, AM, McLaren, J, Shaver, G, and L. Gough. 2017. Long-term nutrient additionalters consumer community composition but does not increase total biomass or abundance. Oikos, 127(3): 460-471. DOI: 10.1111/oik.04398